Thermo-mechanical design and characterization of low dissipation micro-hotplates operated above 500 °C

This work describes the results of a systematic investigation of micro-hotplates capable of operating up to 600 °C both in static and dynamic modes. The goal of development is to form a reduced power consumption micro-pellistor for portable devices. For the selection of optimum device geometry and the membrane layer structure, alternatives FEM analysis was applied. The materials considered were Si3N4, SiO2, TiO2/Pt, Al2O3 and their combination in various multilayer structures. To reduce the chip size DRIE was selected for the release of the membrane. Experimental characterization of the hotplates was carried out by various techniques; the average hotplate temperature was deduced from the resistance of the applied Pt heater and verified by micro-melting point measurements. Buckling of the membranes was tested by means of optical methods and the cumulative stress of the multilayer structure was quantified by Makyoh-topography. Pulsed mode cyclic heating revealed the dynamic properties and also served for accelerated stability tests. For demonstration, micro-heaters with heat dissipation up to 23 °C/mW and t90%<3 ms were constructed. The hotplates were coated with Pt catalyst to form a combustive type gas sensor operated at elevated temperature.